Synchronizing apparatus



March 21, 1950 J. w. LIGHT 2,501,228

SYNCHRONIZING APPARATUS 3 Sheets-Sheet l Filed Oct. 25, 1945 lNVENTO ATTCJRNEYAI.

Patented Mar. 21, 1950 SYNCHRONIZING APPARATUS James W. Light, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application October 25, 1945, Serial No. 624,513 A 3 Claims.

This invention relates to apparatus for synchronizing or equalizing the speed of engine, for example, the engine of a multi-engine airplane. The object of the invention is to provide a synchronizing apparatus which is reliable in operation and simple in construction which can be produced at relatively low cost.

Further objects and advantages of the present invention will be apparent from the following descriptions reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Fig. 1 is a diagram of the apparatus.

Fig. 2 is a side view, in the direction of arrow 2 of Fig. 1, of a device used to vary the governed speed of an electric motor.

Fig. 3 is a plan view of one of the ,units of the apparatus, the part in section being on the line 33 of Fig. 4.

Fig. 4 is a sectional view on the line 4-4 of Fig. 3.

Fig. 5 is a fragmentary, sectional view on the line 55 of Fig. 3.

Fig. 6 is a fragmentary, sectional view on the line 6--6 of Fig. 4.

Fig. 7 is a fragmentary, sectional view on the line l'l of Fig. 6.

Fig. 8 is a view on lines 8-8 of Figs. 1 and 4.

Fig. 9 is a sectional view on the line 9--9 of Fig. 8.

Figs. 10, 11, 12 and 13 are sectional views, taken respectively, on the lines llll0, H--l I, 12-12 and |3-l3 of Fig. 9.

Numeral In designates one engine of a multiengine plane. Engine l drives a shaft H which drives a propeller l2. The speed of the engine is controlled by changing the pitch of the propeller blades by mechanism contained within the propeller hub 13. This mechanism may be of the type shown in the Blanchard and MacNeil Patent No. 2,307,101, issued January 5, 1943. This patent discloses a speed responsive apparatus within the hub for controlling the blade angle to maintain a governed speed which may be varied by a device which includes a lever I4 adjustable about the axis of the shaft H but not rotatable therewith. Lever l4 may be manually actuated by a pilots speed controlling lever l pivoted at l6 and connected by link I! with lever M. For purposes of synchronization, the lever I4 is operated automatically by a mechanism which includes a link I8 connecting lever l4 with a lever l9 connected by a friction clutch 20 connected by shaft 2! with a speed reducing gearing 22 driven by an electric motor 25 which is provided with field windings 23 and 24 which may be selectively energized, in order that the motor may operate in one of two directions.

The field windings 23 and 24 are connected respectively by wires 21 and 28 with pairs of relay contacts 29 and 30 respectively. One contact 29 and one contact 30 are mounted, respectively, on spring blades 3| and 32 iixedat their left ends and connected by a wire 33 and switch 34 and wire 35 with a battery 36. The motor 25 will operate in one direction or the other, depending upon which pair of relay contacts29 or 3; are closed. The spring blades 3| and 32 support armatures 4| and 42, respectively, adjacent magnet cores 43 and 44, respectively, which are surrounded by magnet coils 45 and 46, respectively, paralleled by condensers 41 and 48, respectively. Numeral 49 designates the relay having contacts 29 and numeral 59 designates the relay having contacts 30.

As shown in Fig. 1, the equalization of engine speed is effected by causing the speed of each engine to conform to a speed set by a master electric motor whose governed speed can be regulated. The master electric motor 60 which drives a shaft 6| has a series field winding 62 connected with the non-grounded commutator brush 6% and with a brush B4 engaging a slip ring 65 driven by shaft 6| and connected by wire 66 with a spring blade 61 fixed at B8 and carrying a contact 69 engageable with a contact 10 carried by a spring blade 1| attached to a fixed terminal 12 connected by wire 13 connected with a slip ring 14 driven by shaft 6! and engaged by brush i which is connected with battery 36 by a switchlii. wire 11 and wire 35. The terminals 68 and 52, which together with the contacts and blades are mounted on a non-conducting disc is driven by shaft 6! are connected in parallel with a minimum speed controlling resistance I9 and with a condenser in series with a resistance 8! functioning to reduce sparking at contacts 69 and 10.

At a certain speed which can be adjusted in the manner to be described, contact Hi separates from contact 69 due to centrifugal force acting upon a weight 82 which may be attached, if necessary, to the free end of spring blade Tl. As indicated by the arrow Ha in Fig. 2. blade ll biases contact 10 toward the' right. As indicated by arrow 61a, blade 61 biases contact 69 toward the left end. By varying the initial position of the blade 61. the'speed at which contact 1c will separate from contact 69 can be varied. To vary the position of blade 61 it is connected by link 85 with a lever 86 fixed to a shaft 81 supported by bearing brackets 88 attached to plate 78. Shaft 81 supports an arm 89 carryin button 90 whose axis coincides with the axis of shaft 6|. Button 90 is engaged by a screw 9I threaded through a fixed support 92. If the screw SM is turned so that it moves down in Fig. 2, blade 6! will be pulled toward the right, thereby allowing blade II to move toward the right, thereby reducing its tension or bias in that direction. Therefore the speed at which contact 10 will separate from contact 69 will be relatively low. If screw 9I is turned in the direction so that it moves up in Fig. 2, the opposite effect is obtained, that is, speed at which the contact 10 will separate from contact 69 will be increased. The electric motor with its speed controlling mechanism is not the subject of this application as this type of governed speed motor can be obtained on the market. It is understood that this motor is merely a typical example of a governed speed motor which may be used with the present invention. The screw Si is turned by a flexible cable not shown having a control knob located within the convenient reach of the pilot who can set the governed speed at which all the engines of his plane are synchronized.

The shaft 6| drives slip rings I00, IOI, I02 and I03 connected respectively by conductors I04, I01, I06 and I with certain bars of a commutator II 0, said bars being marked respectively B, I, G, D, said commutator having a plurality of a series of the bars so marked. For

example, as shown in Fig. 8, the commutator may have 30 bars separated by insulation, thereby providing five of each of the bars B, I, G and D with bars I08 and I09 not connected by any slip ring. The end faces of the commutator bars are engaged by brush I20 supported by a non-conducting arm I2I driven by a shaft I22 carrying a slip ring I23 connected with brush I 20 and engaged by a brush I23a connected to a condenser I24 which is grounded. Shaft I22 is driven by a synchronous three-phase motor I25 connected with a three-phase generator I26 having a permanent field magnet I21 driven by the engine I0 through gears I28 and I29.

The shafts 6i and I22 rotate in the same direction, for example, clockwise as viewed toward the left as indicated by arrow 6Ia. If the speed of shaft I22 equals the speed of the shaft 6| neither of the relays 49, 50 is energized. If the speed of the shaft I22 exceeds the speed of shaft M, the brush I20 moves relatively to the commutator H0 in the direction indicated by arrow I20a. Therefore the brush I20 will contact a commutator bar B in advance of contacting a bar blank I09 in advance of contacting an increase pitch bar I. Whenever the bars B are contacted by brush I20, the condenser I24 is connected with the battery and is charged through the followin circuit. Battery 36, wire 35, switch 34, brush I00a, ring I00, wire I04, bar B, brush I20, ring I23, brush I23a, condenser I24. The charging of the condenser is followed by discharge thereof through the following circult: When the brush I20 contacts bars I, a discharge circuit is as follows: Condenser I24, brush I23a, ring I23, brush I20, bar I, wire I01, ring IOI, brush IOIa, winding 45 of relay 49. The relay 49 momentarily closes contacts 29, thereby causing motor 25 to be connected with the battery through the following circuit: Battery 36, wire 35, switch 34, wire 33, blade 3|, contact 29, wire 21, field winding 23 and armature of motor 25. This causes arm I9 to be turned clockwise and lever I4 to be turne counterclockwise in the direction of arrow I4i which is in the direction to increase the pitch of the propeller blade thereby reducing the speed of the engine I0. The greater the over-speed error, the more frequentl will the condenser I24 be charged and then discharged through the relay winding 45. Therefore, the more frequent will be the operations of the motor to correct the speed error by shifting the governor adjusting lever I4 in the direction to increase blade angle. As the correction is made, the engine speed is reduced so that the charging of the condenser I24 and the discharge thereof through relay winding 45 becomes less frequent. In other words, the less the speed error, the less frequent will be the increments of correction of the speed error. Therefore the tendency to over-correct the speed error is minimized. After the brush I20 contacts bar I to effect operation of relay 49 through discharge of condenser I24, it next contacts bar G which is grounded by wire I06, ring I02 and brush I02a. Therefore, there will be no condenser charge carried over into the succeeding decrease pitch bar D which is associated with the engine speed increasing section of the apparatus.

Conversely when the shaft I22 rotates at a speed less than shaft 6|, relative motion between the brush I 20 and the commutator II!) will be that indicated by arrow l20b. Therefore the charging of the condenser when the brush I20 contacts bars B will be followed by discharge of the condenser when the brush contacts decrease bars D through the following circuit: Condenser I24, brush I23a, ring I23, brush I20, bars D, wire I05, ring I03, brush I03a, magnet winding 46 of relay 50. The contacts of relay 50 will close in order to connect the motor 25 with the battery 36 through the following circuit: Battery 36, wire 35, switch 34, wire 33, blade 32, contacts 30, wire 28, field winding 24 and armature of motor 25. The motor 25 will then rotate the arm I9 counterclockwise in order to move the governor adjustin lever I4 clockwise or in the direction of arrow I4d for the purpose of increasing engine speed by decreasing blade angle.

As over-speed or under-speed increases, there will come a time when the rate of relative motion between the brush I20 and the commutator IIO attains a value such that the frequency of discharges of the condenser I24 is such that contacts of either relay remain closed due to the lag which is inherent in the relay. The time lag can be increased in different ways, for example, the relay cores 43 and 44 can be provided with copper slugs or rings 43a, 44a, respectively, or the condensers 41 and 48, respectively, can be used in parallel with the windings 45 and 46 respectively. The function of these condensers is to receive a charge concurrently with the energization of the relay magnet windings and then discharge through the windings as the discharge of the condenser I24 reaches completion. In this way, the relay contacts can be maintained closed upon the attainment of a certain difference in the speed of rotation of the shafts 6| and I22. Therefore, the servo-motor 25 will operate continuously to effect the correction of the speed error of a certain magnitude. Then, as the speed error is reduced, continuous operation of the servomotor 25 is followed by an intermittent operation of diminishing frequency as the speed error approaches zero.

Instead of using lever I to override the control by the synchronizing apparatus, servomotor can be rendered operative independently of the synchronizer. This is effected by movement of a switch handle I in either direction against the action of centering springs I3I in order to close contacts I32 which would connect battery 36 with motor field winding 23 or to close contacts I33 which would connect battery 36 with motor field winding 24.

In a multi-engine installation, four engines,

for example, each engine will be provided with Y the apparatus shown in Fig. 1 except that there will be one master motor 60 for the four synchronizing apparatuses and. one storage battery in an installation where each of the four engines drives a generator for charging the battery. Figs. 3 and 4 show a unitary construction for use in synchronizing four engines. There is a base I40 to which the master motor 60 is attached. A cable I4I extends from the motor to a speed adjusting knob not shown which controls the adjusting screw SI of Fig. 1. As shown in Fig. 4, motor 60 drives a centrally located pinion I42 engaged by idle gears I43 which are rotatably supported by bearings I44 fastened to the frame I40 by screws I45. Gears I43 mesh with gears I46, each on of which drives a shaft I'41 journaled in bearings I48 provided by the frame I40. Each shaft I41 carries the slip rings I00-I03 and the bars of the commutator I I0. Each shaft I41 is in alignment with the shaft synchronous electric motor I25 which rotates a non-conducting arm I2I supporting a brush I20 connected by a strap I20s with the slip ring I23 which is engaged by brush I23a. Figs. 6 and '7 show the manner in which the brushes IBM to I03a are supported. Each brush is slidably supported by a metallic sleeve I50 supported by non-conducting bracket I5I attached by screws I52 to the base I40. A spring I53 within the sleeve I50 urges a brush toward a slip ring. The motors I25 are secured to the base I40 by screws I55 (Fig. 4) each of which passes through motor end frame I56, field frame I51, end frame I58 and spacer sleeve I59. The motors are enclosed by a cover I60 and gears are enclosed by cover I6I. These covers are attached to the frame I40 in a similar manner. For example, the cover I6I, as shown in Fig. 5, is secured to the base I40, by screws I 62 passing through the cover and through spacer sleeves I63 and threaded into bosses I64 out of the base or frame. The cover I60 is secured to the base in a similar manner.

The commutator IIO, as shown in Figs. 8 and 9, has a non-conducting hub I10 of cylindrical formation from which there extends an annular flange I1I received by a notch I12 in each of the commutator bars indicated by the various letters andnumerals heretofore mentioned. As shown in Fig. 8, the bars are spaced by non-conducting segments I13 preferably of mica. The bars and segments are secured around the hub I10 by a non-conducting sleeve I14 which is surrounded by a metal band which after assembly, is divided into the slip rings I00, I'0I, I02 and I03. The band providing the slip rings and the non-conducting band I14 are secured to the bars by metal pins serving the functions of the conductors I04, I05, I06 and I01 of Fig. 1. Fig. 10, which is a section through slip ring I00, shows metal pins pl04 connecting the ring I00 with I22 of a prime movers.

the bars marked B in Fig. 8. Fig. 11, which is a section through the ring IOI', shows pins pI01 connecting ring IOI with the bars marked I in Fig. 8. Fig. 12, which is a section through ring I02, shows pins M06 connecting ring I02 with the bars marked G in Fig. 8. Fig. 13, which is a section through ring I03, shows pins pI05 connecting ring I03 with the bars marked D in Fig. 8. v

In case of a two engine plane where the requirement is to maintain the engine speeds equal to each other rather than to a standard speed, the master motor 60 could be eliminated. Instead, one of the engines would be connected with the shaft 6| and the other engine would be provided with a synchronizing apparatus as shown minus the master motor.

The present invention is not limited in its use to the synchronization of airplane engines but may be used to synchronize various types of In case of steam engines or turbines operating electric generators, for example, the master motor 60 would be adjusted to conform to a standard frequency of electric current such as 60 cycles. The servo-motor 25 associated with each engine would control the engine governing mechanism in order that its governed speed would conform to a speed set by the master motor.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. In a synchronizing apparatus having means for effecting decrease and increase adjustment of engine speed to agree with a reference speed and means for comparing the engine speed with the reference speed and introducing a proper correction in character and amount to the respective engine adjusting means, said comparing means comprising a rotating contact brush driven in proportion to engine speed, a condenser having one plate constantly connected with said brush and a second plate connected to ground, a rotating commutator and slip ring assembly driven in proportion to the reference speed, said commutator having a plurality of contact bars adapted to be sequentially engaged by the said brush upon differentials of brush and commutator rotation, the contact bars of said commutator being arranged in a plurality of groups of bars, means joining a first bar of each group to a'cornmon slip-ring for connection to a current source, means joining a second bar of each group to a second common slip-ring for connection to an engine decrease speed adjusting means, means joining a third bar of each group to a third common slip-ring for connection to an engine increase speed adjusting means, and means joining a fourth bar of each group to a fourth common slip-ring for connection to ground, means for connecting the separate sliprings respectively with a current source, with an engine decrease speed adjusting means, with an engine increase speed adjusting means, and with ground, the sequence of bars in each group being such that differentials in rotation of the brush and the commutator will effect movement of the brush over the bars to first connect the condenser with the current source and then connect the condenser with one of the engine speed adjusting means, and then connect the condenser with a grounding bar before connecting the condenser with the other engine speed adjusting means.

2. In a synchronizing apparatus for shafts of plural engines whose speeds are to be controlled to agree with a fixed speed shaft by means adjusting the speed of the engines to match the speed of the fixed speed shaft, the combination comprising means for sensing the character and amount of speed error for any engine and for signalling the character and amount of correction to be made, said sensing means including a plu rality of commutator assemblies equal in number to the number of engines to be controlled, each commutator assembly including a set of contact bars, each set having a first bar for connection with a current source, a second bar of each set for connection with an engine decrease speed adjusting means, a third bar of each set for connection with an engine increase speed adjusting means, and a fourth bar of each set for connection with a common ground, a plurality of slip rings each electrically connected with like bars of each set, means coincidentally driving all of the commutator assemblies at a speed in proportion to that of the fixed speed shaft, a brush for each commutator assembly continuously rotatable in pro portion to the speed of a separate engine shaft and adapted to engage the bars of the associated commutator assembly, a plurality of condensers each continuously connected between ground and one of said brushes, and means acting upon relative rotation between each brush and its associated commutator for efiecting the sequence of first connecting the condenser to the current source for charging the condenser, then connect ing the C011denser to one of the speed adjusting means to apply the proper correction to the speed of the respective engine, and then connecting the condenser to a grounding connection for completely discharging the condenser before connecting the condenser to the speed adjusting means of improper correction.

3. In rotatable apparatus controlled by reversible speed decrease and speed increase devices upon differential rotation of an adjustable speed member and a fixed speed member, the combination with said members of means for rotating the adjustable speed member in proportion to the rotative speed of the rotatable apparatus, means for rotating the fixed speed member in proportion to a reference speed, a continuously rotating brush driven by said adjustable member, a condenser connected between said brush and ground, said fixed speed member comprising a continuously rotating; commutator having a plurality of sets of contact bars adapted to be individually engaged by said brush, each of said sets including a group of three consecutively arranged mutually insulated bars and a, single bar spaced therefrom and equally spaced from a like group of three contact bars in an adjacent set, a plurality of slip rings and means connecting each ring with all bars of like position in all sets, means connecting said single bar of each set through its connecting slip ring with a current source for charging said condenser when the brush engages any one of said single spaced bars, means connecting an end bar of each group of three as a second bar of said set through its connecting slip ring with a control means for the speed decrease device, means connecting the other end bar of each group of three as a third bar of said set through its connecting slip ring with a control means for the speed increase device, and means connecting the middle bar of each group of three as a fourth bar of said set through its connecting sli ring with a common ground connection for completely discharging said condenser when the brush engages any one of the said fourth bars, the sequence of the four bars of each set being such that relative rotation between the said adjustable speed member and the said fixed speed member effects engagement between said brush and said single spaced bar to connect said condenser with the current source for charging the condenser, and such that continued relative rotation between said members effects engagement between said brush and the said second or third bar to connect said charged condenser with either the speed decrease control means or the speed increase control means respectively, and that further continued relative rotation after said condenser has been connected with either the speed decrease control means or the speed increase control means effects engagement of said brush with the said fourth bar for completely discharging the condenser to ground before the condenser is connected upon furthe continued rotation to either the speed increase control means or the speed clecrease control means respectively.

JAMES W. LIGHT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,553,407 Staege Sept. 15, 1925 1,571,960 Needham Feb. 9, 1926 2,110,015 Fitzgerald Mar. 1, 1938 2,232,751 Wilson Feb. 25, 1941 2,322,114 Clare et al June 15, 1943 2,381,250 Baumann Aug. '7, 1945 2,433,432 Chillson Dec. 30, 1947 2,443,437 Wilson June 15, 1948 

